the system draws from on tank until the switch is flipped then thit activate a module down on the frame rail just behind the cab between the rail & the front tank, that tells witch fuel pump to turn on, wich is likley the cause if your truck will oinly pull fron one tank

well here is the freaky thing. I think it was siphoning fuel from the front tank to the rear tank. I flipped the switch to the front tank and started driving, then i flipped it back to the rear tank and it was full, whereas before i had a quarter of a tank in the rear.

An adjustment to my dual tank issue. The relay box is missing from over left side of wheel well, under hood. Relays just laying on wheel well The 2 square relays (unmarked) are black/brown & black/gre...

I think the rear tank is about 10-12 gal & the gas gauge works on it,but I've no ideal what size the front tank is,& the sending unit goes wild when it gets switched over to the front tank.it goes all...